Follicular Thyroid Carcinoma with Unusual Mandible Metastasis

Metastases to the oral and maxillofacial region are rare, accounting for 1%–2% of all oral and maxillofacial malignancies.[123] Thyroid malignancies account for 2% of facial skeletal metastases.[4] Follicular thyroid carcinoma (FTC) metastasizing to the mandible has been reported in 40 cases, with most cases presenting with clinical complaints and other bone metastases.[56] This case is the 41^st documented case in the literature [Figure 1]. While in most cases in the literature, the first finding was the detection of mandibular metastases in the patient, metastases were only observed in eight cases during the follow-up of FTC. Clinical findings such as pain, facial asymmetry, and swelling were seen in all but four patients, while this case was seen 16 years after the diagnosis of FTC and without clinical complaints.[6] False negatives may be seen in diagnostic iodine scans, one of the reasons for this is the partial volume effect as seen in our case.[7] Metastatic lesions may mimic odontogenic infections or other conditions in the oral region, leading to delayed diagnosis.[89] Nuclear medicine imaging modalities play a critical role in the diagnosis of suspected metastases and have proven particularly useful in cases with elevated thyroglobulin levels.[710] This case emphasizes the need for ongoing surveillance and highlights the potential for unpredictable metastatic patterns in follicular thyroid cancers.

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Figure 1 A 55-year-old woman with follicular thyroid carcinoma (FTC) underwent total thyroidectomy followed by 150 mCi radioactive iodine treatment. Diagnosed 16 years ago and absent for regular follow-ups, the patient had no clinical complaints at the last visit, but laboratory parameters showed thyroid-stimulating hormone: 0.23 mU/L and suppressed TG: 106 ng/ml. Recurrent disease was suspected and a 5 mCi I-131 scan and fluorine-18 fluorodeoxyglucose positron emission tomography/computed tomography (F-18 FDG PET/CT) imaging were performed. I-131 scans showed no suspicious uptake, while F-18 FDG PET/CT imaging showed focal FDG uptake in the left mandibular condyle (SUV_max: 21.4; a-c, arrows). Magnetic resonance imaging demonstrated a 22 mm × 10 mm lesion with peripheral contrast enhancement in contrast-induced T1 series (d), arrows and signal hyperintensities in the T2-weighted sequences (e, arrows). Planar bone scintigraphy and single-photon emission computed tomography/CT (SPECT/CT; f and g, arrows) showed Tc-99 m hydroxymethylene diphosphonate uptake in the same region. Ultrasound-guided fine-needle aspiration biopsy confirmed the malignancy and the patient was diagnosed with a solitary mandibular metastasis of FTC. The patient was again treated with 150 mCi 131-I (stimulated TG value: 240 ng/ml). Posttreatment I-131 planar and SPECT/CT images (h-j, arrows) showed intense iodine uptake, confirming the other images. TG: Thyroglobulin

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